My first attempt at boat design

[ernie]

Defiantly go with the sharpie, do a search for Phil Bolger, he has many examples of what can be done with a sharpie.

I do admire and understand the draw of designing your own boat, but wait till you have the sailing skill to know if a flaw is the boat or the driver.
Once you start building your own designs, you will learn quickly what curves do what, and what is easy to build.

I have been looking at the PD racer, very cool, I will be building one of two soon.


Also as a thought, wouldn’t be in spec for the class, but what would you get if you applied the same curve to the hull sides, to make the for and aft transoms slightly narrower. How would this affect the performance? This would be for a personal dingy, not a class boat.

[frosh]

Hi Ernie, The reason for the straight sides was building simplicity and to build class numbers quickly as a result. In flat water and medium winds the original shape might be better, however in light winds or choppy conditions I believe that pulled in bow and stern transoms would be superior.
In light weather the surface area of the hull bottom is quite large and would be faster if the hull was heeled to leeward. With the class legal shape the immersed section becomes a shocker if it becomes heeled!
In choppy conditions the massive bow transom would be getting hit by solid water considerably, with obvious effect. Wetted surface at the stern of the amount in the class legal shape is excessive and also the stern transom will often be partly immersed, being very draggy, so the width if less, will correspondingly drag less.
However I think that the hull is too short for an adult as well, but was conceived so the bottom is a simple single sheet of ply with no cutting or joining required.

[ernie]

Im thinking of keeping the same curve as the bottom and applying it to the sides.
This should follow Bolgers rule of having the same curve.

another question, would a Brick qualify as a PD? is the curve the same? I will also ask on the duck board.(answered elswhere - NO- thanks)

[BOATMIK]

New website for PD Racers
http://www.pdracer.info

[BOATMIK]

Notwithstanding what has been said above - here are some videos of a PDRacer sailing. Taken since this discussion.

http://www.youtube.com/profile_videos?user=bitingmidge

It sails fine with an adult weight aboard as you can see. Since I wrote the above post we've had them out in 25kn a couple of times - still handle reliably and go upwind fine including a chop.



Not the fastest kids on the block - but a very acceptable starting point. As frosh points out it would have resulted in more performance to change the basic concept - to get a little more speed. And it would have been only a little more speed for lots of messing around.

However one thing we have found is the box shape gives so much stability that you can carry very big rigs. With a good mast/sail combo the more experienced sailors are carrying 82 to 86 square feet.

And the rigs don't need to cost much as the polytarp sails cost around $50 a pop. The blue one you see on the orange boat in the videos is 3 years old with around 60 days sailing under its belt.

The yellow boat above cost $350 to get on the water.

Best wishes
Boatmik

[rwatson]

Frosh - you are right, thats a really nice design, and no harder to build really. And it probably has things like measurements, material lists etc

I think its worth having a look Daywalker, - I would commend the design as a great first project.